I think node-fetch is not encoding non-ascii URLs (which are JavaScript strings) as UTF-8, such as: https://some-server.net/api/thing/diccionario-español/. Making a GET request with fetch() in Firefox/Chrome works as expected but making a GET request on a NodeJS (6.9.4) server with node-fetch does not encode the URL properly. I haven't investigated what the exact discrepancy between the two is but when I added utf8.encode(url) to my NodeJS code, it worked.